The invention relates to a device for picking up, depositing, and transporting thin metal foil sheets by means of a vacuum lifting device and a transport frame which supports the foils.
Vacuum lifting devices are used widely and in manifold arrangements in machines which process paper and synthetic films. However, in the handling of metal foil sheets having a thickness of 2 to 5.times.10.sup.-2 mm, a particular problem consists in that very thin foils of this kind easily curl up when lifted. This is due to the fact that during the rolling of the metal foils, material tensions arise, particularly in the surface zone, and promote a curling or warping of the foils. Even slight movements of air, and likewise the environmental temperature and the atmospheric moisture influence the behavior of the very thin metal foil held on the vacuum lifting device. Under the described conditions it is difficult to deposit a foil flat, for example onto a frame, so as to enable the foil to be transported from one processing station to another. The foil sheets which are to be etched are coated on both sides with a photo-lacquer. They generally bear a plurality of similar motifs which are arranged in rows and columns on the photo-lacquer layer of the foil. A foil of this kind is referred to as a motif mat. The motifs cut out of the motif mat following etching are the motif foils.
In order that the motif mat may be passed through the etching baths, it is necessary for the foil to be elongated and flat (i.e. free from undulations) on the transport frame.